Traditional air filtration systems are not effective for treating many types of microbials (e.g., bacteria, germs, viruses, fungi, spores and mold) and gases (e.g., benzene, formaldehyde, chloroform, hydrogen sulfide, ammonia). Hydroperoxides are very effective at destroying harmful microbials in the air and on surfaces through a process called cell lysing or by changing its molecular structure. Hydroperoxides are also effective at rendering gases harmless by changing their molecular structure. The present invention treats microbials and gases in package air handling units, such as a heating, ventilation and/or air conditioning unit.